- The device can't connect to the Internet service provider (ISP) or to the Internet.
- The device isn't set up correctly.
- The Exchange Online mailbox server that supports the connection isn't available because of maintenance or an outage issue.
- Sign in to the Office 365 portal (https://portal.office.com) as an admin.
- Click Admin, and then click Exchange to open the Exchange admin center.
- In the left navigation pane, click recipients, and then click mailboxes.
- In the list of mailboxes, double-click the user, and then click mailbox features.
- Under Mobile Devices, take the following actions:
- If you see Disable Exchange ActiveSync, this means that ActiveSync is enabled for the user. Go to "Step 2: Confirm that the mobile device isn't blocked by an ActiveSync quarantine rule."
- If you see Enable Exchange ActiveSync, this means that ActiveSync isn't enabled for the user. Click Enable Exchange ActiveSync, click Yes when you're prompted, and then click Save.
- After you re-enable ActiveSync, try to set up the device again.